1. Field of the Invention
The present invention relates to an image recording apparatus that ejects ink droplets to a sheet-shaped recording medium to thereby record an image.
2. Description of the Background Art
Conventionally known is an ink-jet type image recording apparatus that ejects ink droplets to a paper sheet while conveying the paper sheet being held on a holding plate. In this type of image recording apparatus, a plurality of suction holes are formed in the holding plate. The paper sheet is sucked to and held on an upper surface of the holding plate due to negative pressure caused by these suction holes. A head unit for ejecting ink droplets is arranged above a paper-sheet conveying path. The image recording apparatus ejects ink droplets from the head unit while conveying the paper sheet together with the holding plate, to thereby record an image on an upper surface of the paper sheet.
The conventional ink-jet type image recording apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 2009-285871.
In the above-described image recording apparatus, if a paper sheet placed on the holding plate has a size smaller than a region where the plurality of suction holes are distributed, the suction holes are partially exposed around the paper sheet. When the boundary between the exposed suction hole and the paper sheet passes under the head unit, gas sucked to the exposed suction hole causes an airflow toward the suction hole side to occur between the paper sheet and the head unit. This airflow deviates the ink droplet ejected from the head unit, which may cause a defect such as unevenness.
Particularly in a case where the head unit is shaped into a housing so that a lower surface of the head unit is opposed to an upper surface of the holding plate, the above-mentioned airflow is more likely to occur in a gap space between the head unit and the paper sheet. Sometimes, the head unit includes a plurality of ejection ports arranged in different positions with respect to a conveyance direction. Such a head unit is longer in the conveyance direction, and therefore the above-mentioned airflow is still more likely to occur.